1. Field
Apparatuses and methods consistent with what is disclosed herein relate to a relay apparatus, a receiving apparatus and a control method thereof, and more particularly, to a relay apparatus configured to relay a signal received from a transmitting apparatus to a receiving apparatus, a receiving apparatus and a control method thereof.
2. Description of the Related Art
The recent increased demands for various multimedia information of wireless communication systems increased demands for high speed data communication. To meet the demands from the market, the International Mobile Telecommunication (IMT)-Advanced has set the target of improving the current performance of mobile phone systems to 1 Gbps downstream link, and 500 Mbps uplink. The main techniques including Multi Input Multi Output (MIMO), Cognitive Radio (CR) or Coordinated Multi-point (CoMP) are currently researched to achieve the target of improved mobile phone system performance.
The spatial time coding is the efficient technique to reduce degradation of performance of a wireless communication system due to fading. Alamouti suggested a spatial time coding method that can have diversity gains using two transmitting end antennas and a single receiving end antenna. The spatial time coding can maximize the efficiency by being used with an orthogonal frequency-division multiplexing (OFDM) technique, because it does not take selectivity into consideration. Meanwhile, while the spatial time coding using multi-antennas can improve the stability of the communication link and receptivity, there are difficulties associated with need for use of multi-antennas such as power and antenna size problems. Due to the difficulty of establishing a terminal using multi-antennas, the cooperative spatial time coding system using terminals or relays has gained increasing attention. The cooperative wireless communication system has the characteristic of diversity gains through the spatial time coding between a source node and relay node which include a single antenna.
Meanwhile, in a related method that delays a signal at a relay node by the unit of a specific symbol interval and transmits the signal to a receiving node, a simple method of linear amplification and re-transmission is employed. As a result, complexity is low and delay is not included, and the relay node delays the signal by the unit of 1 block to cause the receiving node to have a spatial time block code (STBC) signal, so that the desired symbol is found at blocks in front and back using the STBC signal to obtain diversity gains through the maximal ratio combining (MRC).
However, since accurate symbol estimation is difficult when fading occurs, the method of estimating symbols at the blocks in front and back using inaccurate symbols can cause a problem such as error propagation. Further, full diversity gain is hardly obtained when the receiver estimates symbols, and overhead increases since the relay node separately requires additional subcarriers to distinguish pilots.